Undefined array key "translatable" in _scheduler_translation_validate() (line 732 of modules/contrib/scheduler/scheduler.module)

Can confirm the error in Drupal 10.3.9, Scheduler 2.1.0 version
MR created to fix the error MR !218

This issue is a duplicate of https://www.drupal.org/project/scheduler/issues/3446881 🐛 Unhandled Warning: Undefined array key "translatable" Needs work

Thanks @pcate for the MR and thanks @yevko yes it is a duplicate of the earlier issue 🐛 Unhandled Warning: Undefined array key "translatable" Needs work
However, the steps to repoduce listed here are slighly different, the critical thing is that the Language module needs to be installed, but not the Content Translation module. That makes all the difference and I have now replicated the error.

I have added test coverage on the other issue, and as that is the earlier one, I am closing this as a duplicate. But I will credit the users here on that commit.

jonathan1055 → closed merge request !218